patch 8.2.0110: prop_find() is not implemented

Problem:    prop_find() is not implemented.
Solution:   Implement prop_find(). (Ryan Hackett, closes #5421, closes #4970)
diff --git a/src/evalfunc.c b/src/evalfunc.c
index f192506..003d3b9 100644
--- a/src/evalfunc.c
+++ b/src/evalfunc.c
@@ -620,6 +620,7 @@
 #ifdef FEAT_PROP_POPUP
     {"prop_add",	3, 3, FEARG_1,	  f_prop_add},
     {"prop_clear",	1, 3, FEARG_1,	  f_prop_clear},
+    {"prop_find",	1, 2, FEARG_1,	  f_prop_find},
     {"prop_list",	1, 2, FEARG_1,	  f_prop_list},
     {"prop_remove",	1, 3, FEARG_1,	  f_prop_remove},
     {"prop_type_add",	2, 2, FEARG_1,	  f_prop_type_add},